1. Field of the Invention
The present invention generally relates to a Digital Living Network Alliance (DLNA) system, and more particularly to a method for identifying content update information sent between a Digital Media Player (DMP) and a Digital Media Server (DMS).
2. Description of the Related Art
Home network technology provides a future-oriented home environment in which anyone can receive various high-quality home services when all information appliances in the home are connected to a wired/wireless network, irrespective of place and time. Because this home network technology is regarded as the underlying enabling technology of an ubiquitous environment and is the key technology, research is on-going into ways to improve performance while maintaining quality and scope of services.
One organization whose objectives include improving home network technology is the Digital Living Network Alliance (DLNA), a standardization organization for home network technology. The DLNA solves compatibility problems encountered in commercializing home network products by serving as a standardization organization. The DLNA was created as a result of efforts of an existing Digital Home Working Group (DHWG) created by Microsoft, IBM, HP, Intel, Sony, Matsushita, Samsung Electronics, and others on Jun. 2003. Digital Living Network Alliance and DLNA are registered trademarks of the Digital Living Network Alliance.
The DLNA defines a Personal Computer (PC) Internet network (of a PC, printer, etc.), a mobile network (of a Personal Digital Assistant (PDA), mobile phone, notebook computer, etc.), and an appliance network (of a Television (TV), audio, Digital Video Disc (DVD) player, etc.) as networks coexisting in the home. Moreover, the DLNA has attempted to provide interoperability through three schemes based on cooperation between leading industrial companies, standardization of an interoperability framework, products conforming thereto, and so on.
Specifically, the technology considered by the DLNA is to obtain, transmit, and manage a plurality of digital media contents (e.g., images, music, video, etc.) from personal devices such as mobile devices, PCs, etc. for consumers. That is, the DLNA technology allows media contents to be conveniently enjoyed on a home device, irrespective of the position and the type of device in the home.
For this, the DLNA is developing standards for physical media, network transmission, media formats, streaming protocols, Digital Right Management (DRM), among others on the basis of Universal Plug and Play (UPnP) technology.
Next, the DLNA will be described in detail. First, a network connection in the DLNA is based on Internet Protocol (IP). The IP is the basic network communication protocol for a device operating on the Internet. Through the IP, information can be transparently exchanged by instances of an application program executing on various media.
For example, a PC or Set-Top Box (STB) can wirelessly transmit media contents to a TV of the home through an Institute of Electrical and Electronics Engineers (IEEE) 802.11 Access Point (AP) connected to an Ethernet cable. Accordingly, all DLNA devices can communicate with other devices connected to the Internet through the IP, anywhere in the world.
A physical layer of the DLNA uses at least one of a wired high-speed Ethernet (802.11u) and a wireless Ethernet (802.11a/b/g). The stability of the wired Ethernet has been already verified. The wireless Ethernet has adopted Wi-Fi according to an increase of wireless home network communication.
The technology for discovering and controlling a device within a DLNA network is based on the existing UPnP Audio Video (AV) architecture and the existing UPnP device architecture to automatically configure networking setup for an IP address and identify and manage other devices. Similarly, the technology for discovering and controlling a service within a DLNA network is also based on the existing UPnP AV architecture and the existing UPnP device architecture.
In the above-described DLNA, device classes are divided into a Digital Media Server (DMS) and a Digital Media Player (DMP). The DMS performs a function of a server for providing media in the UPnP AV spec, and the DMP performs functions of a Media Renderer Device (MRD) and a Media Renderer Control Point (MRCP), i.e., functions for selecting, controlling, and playing media.
FIG. 1 illustrates an example of a conventional DLNA system to which the present invention is applied.
As illustrated in FIG. 1, the DLNA system is configured on the basis of a DMS 13 for providing multimedia contents and a Mobile DMP (M-DMP) 11 for executing the provided multimedia contents. The M-DMP 11 conventionally includes wired and wireless DMPs. The M-DMP 11 of the present invention is preferably wireless, but the present invention includes a wired DMP. A Mobile-Network Connection Function (M-NCF) entity 12 used as an intermediate node for coupling the DMP 11 and the M-DMS 13.
In this DLNA system, content update information of the DMS is obtained through a periodic update process after the DMP receives all initial information.
This process will be described with reference to FIG. 2.
FIG. 2 is a flowchart illustrating an example of a process for updating contents of the DMS in a conventional DLNA system.
Referring to FIG. 2, a DMP 21 obtains all information about contents of the DMS 22 through a browse action thereto (Steps 201 and 202).
Through this browse action, a content (or item) list of the DMS 22 is received in Extensible Markup Language (XML) format. Information received in the XML format includes each content Identifier (ID), item tree-related information such as a parent ID, child count, content title, content class, and content size mapped to the associated content, and detailed information about contents.
The update of content information received from the DMS 22 through the browse action is identified in a “ContainerUpdateIDs” event of a “ContentDirectory” (Step 203). In the “ContainerUpdateIDs” event, information about changed items is transferred in a regular period. However, the basic environment of the DLNA system is based on the IP. Because a sequential packet transmission may not be guaranteed according due to the variable traffic of a network environment, a reliability problem occurs in the “ContainerUpdateIDs” event when only a pard if ab updated item is received by the DMS 22.
When an associated event is lost in the “ContainerUpdateIDs” event of the current DLNA content directory spec, information about contents (or items) may differ between the DMS 22 and the DMP 21, i.e., it may be wrong.
When accessing the DMS 22 using this wrong item information, the DMP 21 must wait for a predetermined time because an item cannot be searched for. When the DMP 21 accesses a different item and wrong information or contents, a problem in the associated DMP 21 service occurs. The “ContainerUpdateIDs” event is not an event to be transferred at every update time, but is an event to be transferred periodically. When a content update of the DMS 22 is not transferred in real time, synchronization may not be acquired when the DMP 21 uses a content list.
When update information is lost (Step 204), the conventional DMP 21 obtains all information about contents of the DMS 22 using the browse action (Steps 205 and 206).
When the amount of information lost about contents (or items) of the DMS 22 is small, a special problem does not occur. However, if the amount of information lost about contents (or items) is large as in a computer, significant overhead occurs when all information about contents is fetched by the DMP 21 from the DMS 22 using the browse action. When update information is frequently lost, it significantly affects DNLA system performance.